The warning lights used in blind zone or assisted in lane change in the prior art reflect the light to the desired area from the LED or other light source through the aluminum-plated housing. However, due to the limitations of the existing design of the product itself, the light-emitting area of the product is not smooth, the ratio of the brightest point to the darkest point in the light-emitting area is about 7:1, affecting the consumer's driving experience. For the products having large light-emitting area, multiple light sources or LEDs are to be equipped, increasing costs of product.